Some thoughts and questions on EFI

Jonathan R. Lusky lusky at
Fri May 6 03:31:50 GMT 1994

The_Mechanic writes:
> A couple of quick questions (from an electronics-ignorant ME type guy):
> - the 68HC11 microcontroller chip is an 8 bit unit, right? Is there a 
> similiar chip available in a 16 bit architecture?  Would it even be 
> nescessary?  

Yep, its 8bit.  I'm not sure whats available in 16bit.  I believe the
new GM stuff is ?68333? based.  My EFI Technologies ECU was 16bit, 12mhz
but I don't know what chip.

> - it would be great to develop a system with some accompanying software 
> so that a laptop PC could interface "Real time" with the engine computer.  
> Adjustments could be made "on the fly" with the engine running.  This 
> would be wonderful on the dyno.  Also, an interface that would port 
> information over to the Superflow SF-901 software would also be real 
> cool.  Are these out of reach?
Being able to talk to the ECM with the engine running is a must.  One
nice thing I liked about the Stewart/Stevenson GFI system was its
self-calibration software.  You put the car on the chassis dyno and run
the calibration software, and it graphically displays and array of boxes
representing RPM vs MAP locations.  When the engine is operating at the
MAP,RPM for a box on the screen, that box flashes.  If you mantain that
MAP,RPM, the ECM adjusts the mixture and watches the O2 sensor.  Once it
has spent enough time on that box to get a valid data point, the box on
the screen changes color, and the driver fumbles around with the
throttle and load until he gets to another box, and repeats for all the
boxes that he can get to.  I believe we went thru this 3 times without
EGR & PCV and twice with them.  In one afternoon it was possible to have
a perfect steady state map, with transient response calibration set to
an initial guess and fine tuned on the road.  Of course, with CNG you
can get away with running stoich at high load, so this approach wouldn't
apply to high load with gasoline.  On the other hand, high load could be
done this way I imagine with EGT for feedback instead of O2.

Something else I've seen that I liked was something the EFI-Tech system
had.  There was a interface box that went between the ECU and the
laptop.  ZThe interface box had BIG knobs to adjust fuel (+/- 30%) and
spark (+/- 15 deg) on the fly.  The knobs also functioned without the
laptop connected, although you couldn't tell exactly how much you were
changing things with the laptop and monitor software.

Anyway, this is just food for thought.

Jonathan R. Lusky  --  lusky at
 "Turbos are nice but I'd rather be blown!"
   89 Jeep Wrangler - 258 / pile of junk!
       80 Toyota Celica - 20R / 5spd

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